1. Field of the Invention
The present invention relates generally to a plurality of wireless communication systems, more particularly, to at least one first cellular communication system coexisting with at least one second communication system operating with a lower power in a same area, the said systems operate on the same frequency band. The first and second communication systems negotiate on the resource usage, including frequency, time, and transmit power to mitigate mutual interference and improve the overall system performance.
2. Description of the Related Art
FIG. 1 shows an exemplary layout of two heterogeneous networks operating on the same frequency bandwidth according to the related art. A typical Low Power Node (LPN) is a home eNB (HeNB), while we refer a High Power Node (HPN) as a macro eNB (MeNB), as defined in 3rd Generation Mobile System (3GPP) releases. Both HeNB and MeNB serve a plurality of user equipments (UEs) of its own respectively. The HeNB locate inside the coverage of MeNB. Though there is no direct interference link between the two eNBs, serious interference may occur when a MeNB-served UE (MUE) approaches the vicinity of HeNB. The typical interferences are from HeNB to MUE in the downlink, and from MUE to HeNB in the uplink.
Referring to FIG. 1 (a), the two eNB can exchange information through backhaul, or an interface defined as X2 in 3GPP. There have been mechanisms proposed for ICIC which can be applied in such inter-HPN-LPN interference control. In 3GPP release 8, relative narrowband transmit power (RNTP) indicating the per resource block (RB) transmission power, overload indication (OI) indicating the interference plus noise level per RB, and high interference indicator (HII) indicating future cell-edge UE uplink transmissions, are defined to be exchanged through X2 interface for ICIC.
It is also possible for the LPN and HPN to exchange resource management information over-the-air (OTA). FIG. 1 (b) illustrates an example where the MUE acts as a relay to deliver information between HeNB and MeNB.